Packet Mode Auto-Detection in Multi-Mode Wireless Communication System, Signal Field Transmission for the Packet Mode Auto-Detection, and Gain Control Based on the Packet Mode

1. A method for transmitting a signal field in a wireless local area network, the method comprising: generating a first control sequence and a second control sequence; generating a first pilot sequence and a second pilot sequence; generating a first modulation sequence by modulating the first control sequence on a first binary phase shift keying (BPSK) constellation; generating a first modulation pilot by modulating the first pilot sequence on the first BPSK constellation; generating a second modulation sequence by modulating the second control sequence on a second BPSK constellation; generating a second modulation pilot by modulating the second pilot sequence on the first BPSK constellation; transmitting the first modulation sequence and the first modulation pilot in a first orthogonal frequency division multiplexing (OFDM) symbol; and transmitting the second modulation sequence and the second modulation pilot in a second OFDM symbol, wherein the second BSPK constellation is rotated by 90° counter-clockwise relative to the first BPSK constellation.

2. The method of claim 1 , wherein signal bits representing control information are divided into the first control sequence and the second control sequence.

3. The method of claim 2 , wherein the signal bits include a first field indicating whether or not a space time block code is used, a second field indicating a number of spatial streams, and a third field indicating whether or not a short guard interval is used.

4. The method of claim 1 , wherein a transmission bandwidth at the first OFDM symbol is substantially the same as a transmission bandwidth at the second OFDM symbol.

5. The method of claim 4 , wherein the transmission bandwidth is one of 20 MHz, 40 MHz, 80 MHz, and 160 MHz.

6. An apparatus of transmitting a signal field in a wireless local area network, the apparatus comprising: a memory; and a processor operatively coupled to the memory and configured to: generate a first control sequence and a second control sequence; generate a first pilot sequence and a second pilot sequence; generate a first modulation sequence by modulating the first control sequence on a first binary phase shift keying (BPSK) constellation; generate a first modulation pilot by modulating the first pilot sequence on the first BPSK constellation; generate a second modulation sequence by modulating the second control sequence on a second BPSK constellation; generate a second modulation pilot by modulating the second pilot sequence on the first BPSK constellation; transmit the first modulation sequence and the first modulation pilot in a first orthogonal frequency division multiplexing (OFDM) symbol; and transmit the second modulation sequence and the second modulation pilot in a second OFDM symbol, wherein the second BSPK constellation is rotated by 90° counter-clockwise relative to the first BPSK constellation.

7. The apparatus of claim 6 , wherein signal bits representing control information are divided into the first control sequence and the second control sequence.

8. The apparatus of claim 7 , wherein the signal bits include a first field indicating whether or not a space time block code is used, a second field indicating a number of spatial streams, and a third field indicating whether or not a short guard interval is used.

9. The apparatus of claim 6 , wherein a transmission bandwidth at the first OFDM symbol is substantially the same as a transmission bandwidth at the second OFDM symbol.

10. The apparatus of claim 9 , wherein the transmission bandwidth is one of 20 MHz, 40 MHz, 80 MHz, and 160 MHz.